Home power lines usually use a single-phase three-wire system having first and second “hot” lines L1, L2 and a neutral that sends power to each home from a distribution transformer. Usually, several homes share one distribution transformer. Power lines L1 and L2 are normally coupled together (and usually coupled to neighbors) via the distribution transformer. Power line communication (PLC) networks utilize the existing power lines in order to facilitate computer networking (or networking of other appliances such as audio/video equipment). In one example, networks using the HomePlug® standard are used for achieving PLC communication. Since such networks interconnect devices using existing power outlets, information traveling over the power line may be accessible by neighbors or others tapping into the power line outside the home. If filtering is installed to prevent data from traveling outside the home, the two lines L1 and L2 may be isolated from each other.
In the case of global communication between lines L1 and L2, the signal may travel a long distance and get attenuated. Although attenuation in global communication is often negligible, sometimes it is not and thus it requires high transmission power, which would cause interference to other electronic products.